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Beamline design

SOLABS is a compact beamline without Al or Be windows, which commonly are used to protect the vacuum of the storage ring.

The only window in the beamline is a thin polypropylene foil between the monochromator and the first ionization chamber. This beamline design allows challenging XAS measurements at low photon energies, e.g., at the Al K absorption edge.

Due to this straightforward and user-friendly concept without any additional optical components such as lenses or mirrors, SOLABS can be quickly aligned and easily operated. 

 

Beamline optics

In the front end section, the synchrotron beam is defined by two fixed apertures. Downstream from SOLARIS´ radiation shield wall a diagnostic module with a fluorescence screen and a wire-type X-ray beam position monitor (XBPM) allows to visualize and determine the position of the white beam and its profile.

A compact differential ion pump maintains the pressure difference of 4–5 orders of magnitude between the diagnostic module (ultra-high vacuum chamber, base pressure in the 10-10 mbar range) and the monochromator (high-vacuum system, 10-6 mbar range).

The monochromator is a modified Lemmonier type double crystal monochromator (DCM). The first and second crystals are mounted parallel on a motorized rotation stage (range ~ 15° - 65o) driven by a stepper motor (angular resolution ~ 0.0001°). The Bragg axis rotation is mechanically linked to a translation of the second crystal perpendicular to its surface via a fixed curved cam, providing a fixed position of the exit (monochromatic) beam during energy scanning.

 

 

Double crystal Monochromator: Photo (up) and scheme, which illustrates how it works (down)

The energy range of the beamline will be covered by 5 sets of crystals: Ge (220), Si (111), InSb (111), Beryl (10-10), and organic potassium acid phthalate (100) + multilayer. Since the DCM is a high vacuum system, opening its vacuum chamber for changing crystals and pumping down to the base pressure takes less than 1 hour.  Thus, the crystals, i.e., working energy ranges, can be changed a few times per day.

Energy range (keV)

Crystal

2d spacing (Å)

Accessible K absorption edges

Beam size at sample FWHM

(hor × ver)

Flux at sample (ph/sec) at 300 mA

0.5 – 1.8

KAP (100) + multilayer

26.63

Na, Mg, Al

Coming soon!

Coming soon!

0.85 – 1.6

Beryl (10-10)

15.95

Na, Mg

Coming soon!

Coming soon!

1.8 – 3.7

InSb (111)

7.48

Si - K

Coming soon!

Coming soon!

2.0 – 7.6

Si (111)

6.27

P - Fe

Coming soon!

Coming soon!

3.4 – 12.0

Ge (220)

4.00

K - Se

Coming soon!

Coming soon!

 

 

XAS end station

After beamline commissioning (summer 2021) X-ray absorption spectroscopic experiments will be carried out in transmission mode. Implementation of fluorescence mode measurements (for inhomogeneous and diluted samples) will follow. Moreover, as future upgrades surface-sensitive Total and Conversion Electron Yield (TEY, CEY) measurements are planned.